Utility knives are widely used for a number of different purposes and are a very popular and handy tool. Conventionally, utility knives use a thin double-ended blade. In use one end of the blade extends out one end of the knife case, and when the cutting end becomes dull or otherwise unsuited for continued use, the blade is reversed so that its other end extends out of the case. With most utility knives, reversal of the blade requires handling of the blade, and because the blades are very sharp, thin, and not particularly easy to handle, accidents frequently occur. It is also difficult to properly mount the blade within the case.
A number of utility knives have been developed that employ cartridges that hold a plurality of blades, some of which enable the user to change the blade with a reduced risk of cutting ones self, but none have proved to be entirely satisfactory. Some require a very large case to receive the cartridge, which detracts from the comfort and convenience of using the tool. And none of the prior art tools known to applicant provide total protection against accidental injury when reversing or changing the blade. Many of those knives have non-traditional shapes so as to limit their appeal to those who in the past have frequently used the convention knife.